1. Field of the Invention
The present invention relates to a magnetic head slider used for a magnetic disc unit and a manufacturing method therefor.
In recent years, the magnetic disc unit has been made compact, its performance has been highly enhanced, and its cost has been reduced. In accordance with this recent tendency, it is desired to develop a thin film magnetic head of high performance and low cost. In order to meet the demand, a horizontal magnetic head (planar magnetic head), is proposed in which a thin film pattern forming surface is arranged in parallel with a flying surface. The reason is described as follows. In the case of a horizontal magnetic head, it is easy to form flying rails having specific shapes. Therefore, it is possible to realize a magnetic head capable of flying stably close to the disc surface, and further it is easy to reduce a portion to be machined in the manufacturing process. Therefore, the cost can be lowered.
In accordance with an increasing demand for enhancing the density of magnetic recording and also in accordance with an increasing demand for reducing the sizes of the head element and the magnetic head slider, problems occur in machining and handling.
2. Description of the Related Art
For the above reasons, there has been proposed a magnetic head slider which can be manufactured without being machined. This magnetic head slider is disclosed in Japanese Unexamined Patent Publication No. 9-81924, the title of which is "Thin film magnetic head slider and electrostatic actuator thereof".
The above prior art will be explained below.
FIGS. 1(a) to 1(c) are views showing a thin film magnetic head slider of the prior art. FIG. 1(a) is a perspective view of the slider 10 attached to the head suspension 30, seen from the flying surface side. FIG. 1(b) is a perspective view of the slider 10, seen from the back (opposite side to the flying surface) thereof, before the slider 10 is attached to the head suspension 30. FIG. 1(c) is a cross-sectional view taken on line B-B' in FIG. 1(b).
A portion of the flying surface layer (air bearing surface) 11 made of SiO.sub.2 or Al.sub.2 O.sub.3 protrudes onto the flying surface side of the slider 10 which is opposed to a recording medium not shown in the drawing. This protruding portion forms two flying rails 15 which extend from the inflow end 13 to the outflow end 14 with respect to the recording medium moving in the direction of arrow A. On the leading end 13 side between the two flying rails 15, there is provided a central rail 17. Metallic plating of Ni is conducted on the main body 12 of the slider 10 formed on the back of the flying surface layer 11, and also metallic plating of Ni is conducted on the terminal pad section 18 shown in FIG. 1(b).
The element drive mechanism section 20 (tracking mechanism) is formed in a portion between the two flying rails 15 and also between the terminal pad section 18 and the trailing end 14. That is, the portion of the tracking mechanism section 20 is subjected to plating of Ni in the same manner as that of the main body 12 of the slider 10.
As shown in the cross-sectional view of FIG. 1(c), the tracking mechanism section 20 utilizes an electrostatic attraction force. The moving piece is composed of two parallel springs 21 (only one spring is shown in the drawing) extended from the stationary section and an element mount section 22 supported at the forward end of the parallel springs 21. The parallel springs 21 of the movable piece and the stationary piece 23, which is opposed to the parallel springs 21, are made of a metal such as Ni or Cu. Alternatively, the movable piece and the stationary piece are respectively provided with metallic electrodes at the portions opposed to each other. When voltage is impressed between the stationary piece electrode 23 and the movable piece electrode 21, an attraction force is generated, so that tracking can be conducted by the attraction force.
In this connection, concerning the movable piece, only the head element 24 or the forward end 24a of the magnetic pole of the head element is protruded onto the recording medium (not shown) side. Therefore, the drive electrode sections 21, 23 are separate from the recording medium. The reason is to avoid an influence of the drive section on the flying force of the slider 10 and also to avoid the attraction of dust to the head element 24 by the voltage impressed between the electrodes 21, 23.
FIG. 2 is a view showing another example of the electrostatic actuator of the prior art. The outer frame is composed of a stationary section 31 which is formed by means of plating of Ni. On the inner wall of the stationary section 31, there are provided teeth 31a which are arranged toward the inner circumference in parallel to each other. These teeth 31a are formed by means of plating of Ni simultaneously when the stationary section 31 is formed. These teeth 31a may be fixed to the substrate, or alternatively these teeth 31a may be arranged in such a manner that a gap (not shown) may be formed between these teeth 31a and the substrate. A central portion located inside the stationary section 31 is the movable section 32 formed by means of plating of Ni simultaneously when the stationary section 31 is formed. The movable section 32 is arranged in such a manner that it can be relatively moved with respect to the stationary section 31 while a gap (not shown) is provided between the movable section 32 and the substrate. In the movable section 32, there are provided a plurality of teeth 32a at positions shifted from the centers of the teeth 31a, which are arranged in parallel to each other in the stationary section 31, and these teeth 32a are arranged in parallel to the teeth 31a. In the drawing, at an upper portion and a lower portion of the movable section 32, there are provided supports 33 fixed to the substrate, and also there are provided support springs 34, by which the movable section 32 can be moved only in the upward and downward direction in the drawing, between the supports 33 and the movable section 32. Lead wires 35, 36, to be connected to terminals not shown in the drawings, are formed by means of plating of Ni at the right lower portion of the stationary section 31 and the support on the lower side.
When voltage is impressed between the two lead wires 35, 36, an electrostatic attraction force is generated between the teeth 31a of the stationary section 31 and the teeth 32a of the movable section 32. The movable section 32 is attracted upward by this electrostatic attraction force and moved to a position at which the electrostatic attraction force is balanced with a restoring force of the support spring 34. Since the attraction force is proportional to the square of an electric potential difference, the movable section 32 is moved in the same direction irrespective of the polarity.
In order to prevent the occurrence of a short circuit at the teeth 31a of the stationary section 31 with the teeth 32a of the movable section 32 when an excessively high voltage input is given, a stopper 37 is arranged in a portion of the support 33 by reducing a gap between the support 33 and the movable section 32.
Next, referring to FIGS. 3 to 5, a method of manufacturing the magnetic head slider of the above conventional example disclosed in Japanese Unexamined Patent Publication No. 9-81924 will be explained below. FIG. 3 is a view showing a magnetic head slider of another conventional type. However, only the shape and arrangement of the rails are different from those of the magnetic head slider shown in FIG. 1(a), and the manufacturing method is the same. FIG. 4 is a cross-sectional view taken on line C-C' in FIG. 3, and FIGS. 5(a) to 5(d) are views showing a manufacturing process.
In FIG. 3, this magnetic head slider conducts reading and writing in such a manner that the electrostatic actuator 40a (from the protective layer 41 to the actuator layer 44), on which the horizontal head element is mounted, drives in the tracking direction (direction X in FIG. 3), so that the magnetic slider follows a track on the medium (not shown in the drawing). Since the magnetic head slider follows the track, the track pitch can be reduced and the recording density can be enhanced.
The electrostatic actuator 40a can be moved upward and downward (direction Z in FIG. 3), so that the head element can be loaded and unloaded. That is, when reading and writing is conducted, the head element 43 is made to come close to a recording medium, i.e., closely flying on it, or alternatively the head element 43 is made to come into contact with the recording medium. At any other time, the head element 43 is separated from the recording medium. Since only the head element 43 is made to come close to the recording medium, it is possible to ensure a flying distance of the slider 40 itself, and the recording density can be enhanced while the slider 40 is stably flying above the recording medium.
A method of manufacturing the actuator of this magnetic head slider 40 will be explained as follows.
(1) A sacrifice layer 51 (for example Al film) is formed on the substrate 50, and a protective layer 41 (for example, diamond-like carbon (DLC) film) and a flying surface layer 42 (for example, SiO.sub.2 film) are formed on the sacrifice layer 51 as shown in FIG. 5(a).
(2) A hole 52 is formed, so that the hole 52 penetrates the flying surface layer 42 and the protective layer 41 and stops on the sacrifice layer 51. In order to form this hole 52, for example, ion milling or reactive etching is used as shown in FIG. 5(b).
(3) A head element 43 is formed so that a leading end portion of the head element 43 can come into hole 52 as shown in FIG. 5(c).
(4) An actuator layer 44 and a slider body 45 are formed by means of plating (for example, plating of Ni) on the head element layer 43 via a plated base. Due to the foregoing, a magnetic head slider 40 having an actuator is formed on the substrate 50 as shown in FIG. 5(d).
(5) When the sacrifice layer 51 is removed by etching, for example, by etching in a solution of KOH, the magnetic head slider 40 is separated from the substrate 50. In this way, the magnetic head slider 40 can be completed as shown in FIG. 4.
At this time, on the surface of the slider 40 which is opposed to a recording medium, a forward end portion of the head element 43 protrudes to the same surface as that of the protective film 41.
In this connection, the actuator layer 44 in FIGS. 4 and 5 corresponds to the head mounting section 22 shown in FIG. 1(c) or the movable section 32 shown in FIG. 2. The actuator layer 44 supports the head element so that the head element can be moved in the tracking direction (direction X in FIG. 3) and the upward and downward direction (direction Z in FIG. 3 which is the loading and unloading direction) as described before.
Another prior art device is disclosed in Japanese Unexamined Patent Publication No. 8-203053. According to this prior art reference, the contact force of the magnetic head with the magnetic disc, which is a recording medium, is controlled. In order to keep the contacting condition of the magnetic head with the magnetic disc stable, an air gap is formed between the primary slider and the auxiliary slider, and the intensity of the contact force of the magnetic head slider with the magnetic disk is adjusted by controlling the voltage impressed upon the electrode provided in the air gap.
According to still another prior art reference, Japanese Unexamined Patent Publication No. 9-22519, in order to read and write on a magnetic disk of high track density, an inching mechanism by which a recording element and a reproducing element can be relatively moved, is provided.
In the magnetic head slider described in the above Japanese Unexamined Patent Publication No. 9-81924, when the electrostatic actuator 40a is loaded and unloaded, the head element 43 is made to come close to the recording medium. When the head element 43 contacts the recording medium, the entire electrostatic actuator 40a comes into contact with the recording medium, and reading and writing is conducted by the head element 43. When the head element 43 is made to come close to the recording medium, a collision occurs. At this time, the same thing as that caused in the case of contact occurs. At this time of contact, when the electrostatic actuator 40a is driven into the tracking direction, a frictional force is caused resisting the drive force of the electrostatic actuator 40a.
On the other hand, reading and writing is conducted in such a manner that the electrostatic actuator 40a drives the head element 43 in the tracking direction so that the head element 43 can follow the track on the recording medium. Therefore, it is preferable that the intensity of the load or the resistance is as low as possible. However, the above frictional force sufficiently resists the drive force of the electrostatic actuator 40a . Therefore, the quantity of displacement is decreased by the resistance of the frictional force. For the above reasons, it is impossible for the head element 43 to follow the track accurately.